Oscillation generator system



A ril 13, 1926. 1,580,447

J. SLEPIAN OSCILLATION GENERATOR SYSTEM Filed April 21; 1921 flLTNESSES! INVENTOR M {eseph ilepian.

4 C 44 ATTORNEY Patented Apr. '13, 1926.

U-NITEQ STATES PATENT" OFFICE.

JOSEPH SLEPIAN, OF WILKINSBUBG, PENNSYLVANIA, ASSIGNOB TO'WEBTINGHOUSE ELECTRIC 8:: MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

oscrnnnr'ron GENERATOR sysrzu.

i Application fled April 21, 1921. Serial-Ho. 468,210.

To all whom it may concern:

Be it known that I, JOSEPH SLEIIAN, a citizen of the United States, and a resident of \Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Oscillation Generator Systems, of which the following is a specification.

My invention relates to thermionic devices and particularly to externally controlled thermionic devices which may be employed as oscillators in, oscillation-generator systems. The object of my invention is to provide an electrical system whereby the negative charges which have hitherto formed on the inner walls of thermionic devices employing an external control electrode are caused to be formed upon the external electrode itself where the rate of leakage of the charge therefrom may be selectivelycontrolled.

In the normal operation of three-electrode vacuum tubes employing an external control electrode, which is so disposed that the field of force therefrom is substantially parallel to the space-current path between the elec trodes within the vacuum tubes, it has been found that the inner surface of the vacuum tube acquires a mean negative charge.

Furthermore, it has been found that. in the operation of such devices as detectors, amplifiers, or oscillators, a close adjustment of the rate of leakage of the charge from the inner walls of the vacuum tube is re quired for the most efficient operation thereof. The rate of leakage of the charge has been found, experimentally, to depend, among other things, upon the residual gas within the tube, the filament current and the plate voltage.

It is evident that the rate of leakage of the charge from the inner surface of the walls of such tubes is not subject to close control in the manufacture thereof, so that the adjustment of the leakage must be effected by varying the filament temperature and plate voltage. The disadvantage, however, of so adjusting the leakage, is that there is a tendency for the working adjustment of the tube to become critical in value.

According to my invention, I provide means whereby the negative charge is caused to form on the external control electrode rather than on the inner walls of the tube, and, in addition, means are provided for selectively controlling the rate of leakage of the negative charge.

The negative charge is prevented from forming on the inner surface of the tube by shunting the control electrode and the filament with an electron valve which is so connected that the grid is prevented from assuming positive potentials withsrespect to the filament, the electrons being attracted to the inner surface of the walls of the tube only when the control electrode is positive with respect to the filament. I

A condenser is inserted in series with the external control electrode or grid circuit to admit of the electrode acquiring and maintaining a mean'negative potential during the operation of thetube as an oscillator.

The rate of leakage "of the charge so formed on'the control electrode is varied by a grid leak which affords a path over which the charges on the condenser and grid may pass to the filament.

Other'objects, as well as details of con-- struction, whereby my invention may be car- 'ried out, will be apparent from the following description, taken in connection with the accompanying drawings and claims, wherein;

- rangement shown, the control electrode 4 is so disposed that the field of force between the hot cathode 2 and the control electrode 4 is substantially parallel to the field of force between the hot cathode 2 and the anode 3,

though I do not wish my invention to be limited to such an arrangement of elements.

ment circuit and the grid-filament circuit is \1! that existing between the portions 7 and 12 of the tuning coil-8. A single condenser 13, which is connected to points on the portions 7 and 12 of the tuning coil 8, may be employcd to tune the grid-filament and platefilament circuits simultaneously.

The plate-filament circuit is energized by means of a source of direct-current energy 14:, which is connected in shunt relation to the anode 3 and the hot cathode 2, through a conductor 15 and a reactor 16. The grid or control electrode 4 is prevented from assuming a positive potential with respect to the hot cathode 2 by means of a thermionic valve 17 which comprises an anode 18 and a hotcathode 19. The anode 18 is connected to the control electrode 4 by means of a conductor 21. The hot cathode 19 is connected to the hot cathode 2 and is also energized by the source of energy 5.

The rate of leakage of the charge from the grid 4 is controlled by means of a variable resistor 22 which, for purposes of illustration, has been shown as directly connecting the grid 4 and the hot cathode 2, though it is equally effective when connected in any other manner that affords a path over which the condenser 11 may discharge. The resistance 22 and the tube 17 are in shunt to each other and may also be regarded as in shunt to the conductor 9, inductor l2 and condenser 11, in series.

Having thus described the elements of the system embodying my invention, the opera tion thereof is as follows:

Assuming the grid leak 22 and the thermionic valve 17 removed from the system shown in the drawing, upon the supply of energy to the plate-filament circuit, the tube functions as an oscillation generator. As hereinbefore stated, during the first assumption of a positive potential by the grid 4, large numbers of electrons are attracted to the inner surface of the walls of the tube forming negative charges thereon. The potential variations of the grid 4 with respect to the filament 2 are, therefore, effected above and below some mean negative value which is determined by the negative charge on the inner surface of the tube.

\Vith the arrangement of circuits, as shown in the drawing, however, upon the tendency of grid 4 to assume a positive potential with respect to the filament 2, the electron valve '17 becomes effective as a short-circuit path. Thus, by preventing the grid 4 from assuming a positive potential, with respect to the filament 2, substantially no electrons are attracted to the inner surface of the walls of the tube.

In order to cause the grid 4 to assume a mean negative potential, such as is effected by the negative charge ordinarily formed on the innner walls of the tube 1, I have provided a condenser 11 in the gridrfilament circuit. The rate of leakage of the negative charge so formed may readily be controlled by means of the resistor 22.

The advantage of my invention resides in the provision of simple and efiicient means whereby the rate of leakage of the negative charges from tubes employing external control electrodes may be readily adjusted to such values as are necessary to effect efficient operation of the tubes as detectors, as amplifiers or as oscillators.

\Vhile I have shown my invention as applied to a particular arrangement of circuits. I do not wish to be limited thereby but I desire that only such restrictions shall be placed upon my invention as are set forth in the appended claims.

I claim as my invention:

1. The combination with an evacuated electric device having a space-current path therein, of electrostatic means for preventing the formation of a negative charge upon the inner surface of the walls thereof.

2. The combination with an evacuated electric device having a space-current path therein and an external control electrode, of means for preventing the formation of positive charges upon said control electrode.

3. The combination with an evacuated electric device having a space-current path therein and an external control electrode, of

means for causing said external control electrode to assume a mean negative charge, and means for varying the value of said mean negative charge.

4. The combination with a vacuum-tube device having therein a cathode and an anode, of an external control electrode therefor, and a rectifying device connected in shunt to said cathode and said control electrode.

5. The combination with a vacuum-tube device having therein a cathode and an anode, of an external control electrode therefor, means including a rectifying device for causing said control electrode to assume a mean negative charge, and means for controlling the rate of leak of said charge.

6. An oscillation-generator system comprising an evacuated electric device having a space-current path therein, means for causing said evacuated electric device to function as an oscillation generator and means outside said space-current path for preventing the formation of negative charges on the inner surface of the wall of said evacuated electric device.

7. Anoscillation-generator system comprising a vacuum-tube device having therein a hot cathode and an anode, an externalcontrol electrode disposed adjacent the exterior surface of. said vacuum-tube device,

means for causing said vacuum-tube device to function as an oscillato-r, and a rectifying devlce c nnec ed in h nt to said hot cathode and said control electrode whereby negative charges are prevented from forming on the inner surface of said vacuum-tube device.

8. An oscillation-generator system comprising a vacuum-tube device having a spacecurrent path therein, electrodes individual to said space-current path, an external-control electrode disposed adjacent the exterior sur face of said vacuum-tube device, means for causing said tube to function as an oscillator, a thermionic valve connected in shunt to said external-control electrode and one of said electrodes for preventing the formation of negative charges on the inner surface of said vacuum-tube device, means for causing the formation of a mean negative charge on the external electrode, and a resistor connected in shunt to said control electrode and one of said electrodes for controlling the rate of leakage of said negative charge. 9. In an electrical system, the combination with an evacuated electric device having a filament and an anode therein and a control electrode disposed immediately adjacent the external surface of said evacuated electric device, of a tuned plate-filament circuit including a coupling coil, a grid-filament circuit including a condenser and a coupling coil, said coupling coils being mutually inductive, means for energizing said plate-filament circuit, and a resistor and a thermionic valve connected in a shunt circuit around a portion of said grid-filament circuit including said condenser, said thermionic valve being so connected as to prevent the formation 01 positive charges upon said control electrode.

10. In an electrical system, the combination .with an evacuated electric device having a hot 'filament and an anode therein, means for producing an electron stream therebetween, and an external control electrode so disposed that the field of force therefrom is substantially parallel to said electron stream, of a tuned late-filament circuit including a coupling 0011, a grid-filament circuit including a condenser and a coupling coil, said coupling coils being mutually inductive,

around a portion of said grid-filament cir-- cuit including said condenser, said thermionic valve being so connected as to prevent the formation of positive charges upon said control electrode.

11. The combination with an electron tube having an enclosing vessel and means for establishing a space-current path therein, of an externally disposed control electrode, a control circuit including a condenser in series with said control electrode, and means for producing the effect'of a grid leak in a shunt circuit around a portion of said control circuit, said portion including said condenser.

12. An electron tube comprising an enclosing vessel, a cathode and an anode constituting two internal electrodes therein, means ,including an externally disposed electrode,

for producing a controlling electrostatic field, one of said internal electrodes being disposed between said external electrode and the other internal electrode, and means for substantially preventing said external electrode from accumulating a positive charge with respect to said cathode.

13. In a vacuum-tube device, a container having internal electrodes and an external electrode, means cooperating with said electrodes for impressing a periodically alternating potential on said external electrode, whereby the potential of said-external electrode tends to alternate, and'means for maintaining said external electrode at a potential corresponding to the amplitude of onesign only of said periodic potential, whereby the mean potential of said external electrode is given a predetermined sign.

In testimony whereof, I have hereunto subscribed my name this 14th day of April JOSEPH SLEPIAN. 

